Method and apparatus for embedding a chip in a substrate to form a composite air bearing surface

BACKGROUND

1. Technical Field

The present invention relates to heads used to write and retrieve information on magnetic storage tape media. More particularly, the invention concerns a method for embedding a chip that has active elements, in a substrate, to form a composite air bearing surface that may be used, for example, in a tape head.

2. Description of Related Art

Magnetic tape is widely used for storing data in computing systems. Tape heads are used for writing information to the tape and reading information from the tape. A tape head typically includes two modules that each have a plurality of reading and writing elements, that may be called active elements. In each module, the reading and writing elements are formed in a substrate that has a smooth air bearing surface (ABS) which makes contact with and supports the flexible tape as it travels. This type of tape head may be called a contact recording tape head. To minimize the occurrence of decreased signals from spacing losses, damage to the tape, and other problems, the air bearing surface of each module must be very smooth, so that the tape can pass over each module in close proximity to the reading and writing elements. Because of its degree of smoothness, an air bearing surface may be referred to as being optically polished.

Because the reading and writing elements in each module span only a small portion of the tape width, during operation the tape head is moved laterally so that the substrate in each module moves laterally across the tape to line up the reading and writing elements with the tracks on the tape that are being read from or written to. Consequently, the substrates are wider than the width of the tape, and are considerably wider than the portion of the tape spanned by the reading and writing elements, to maintain support of the tape surface and to avoid potentially tearing the tape with sharp edges while lining up the reading and writing elements with tracks that are not in the center of the tape.

Traditionally, the reading and writing elements and the substrate of a module are formed in a semiconductor wafer. Forming the substrate in the wafer requires a much larger area of the wafer than is required for the reading and writing elements. Due to the high cost of wafer space, forming the substrate in the wafer substantially increases the cost of making a module. Consequently, existing methods for making tape heads are not completely cost effective.

SUMMARY

One aspect of the invention is a method for embedding a chip in a substrate, to form a composite air bearing surface. An example of the method includes securing the substrate in a fixed position, and aligning the chip in a first direction with a chip receiving slot in the substrate. The method also includes depositing adhesive in the chip receiving slot in the substrate, and aligning the chip in a second direction with the chip receiving slot in the substrate. The chip is then pushed into the adhesive in the chip receiving slot. The method further includes detecting when an air bearing surface of the chip is substantially at a desired protrusion in a third direction in relation to an air bearing surface of the substrate. Responsive to detecting that the air bearing surface of the chip is substantially at the desired protrusion in the third direction in relation to the air bearing surface of the substrate, the operation of pushing the chip into the adhesive is ceased. The adhesive is at least partially cured to bond the chip to the substrate with the air bearing surface of the chip substantially at the desired protrusion in the third direction, and with the chip substantially aligned in the first and second directions with chip receiving slot in the substrate.

Another aspect of the invention is a tape head read/write module that has a composite air bearing surface. The module includes a substrate that has an air bearing surface, a front, a back, and a chip receiving slot. The chip receiving slot has a front at the front of the substrate, a back at the back of the substrate, a first side, a second side, and a bonding surface. The air bearing surface of the substrate has a first portion adjoining the first side of the chip receiving slot, and a second portion adjoining the second side of the chip receiving slot. The module also includes a chip that has an air bearing surface, a bottom surface, a front, a back, and active elements. The active elements are located proximate to the front of the chip. The chip is inserted in the chip receiving slot in the substrate, with the air bearing surface of the chip substantially aligned with the air bearing surface of the substrate, and with the back of the chip substantially aligned with the back of the substrate.

Other aspects of the invention are described in the sections below, and include, for example, an apparatus for aligning and bonding a chip with a substrate to form a composite air bearing surface.

The invention provides a number of advantages. The invention permits making a composite air bearing surface by embedding a chip that has reading and writing elements, in a substrate, which makes it unnecessary to form the substrate in the expensive semiconductor wafer with the chip. Because the substrate is much larger than the chip and is not made in the wafer, a larger number of chips can be made in the wafer, which advantageously reduces the cost of each chip. Additionally, a larger number of chips can be produced in each row on the wafer, and consequently, the lapping cost per chip is lowered because a larger number of chips can be simultaneously lapped. Further, the composite air bearing surface does not require lapping after the chip is embedded in the substrate, which can be an expensive operation. The invention also provides a number of other advantages and benefits, which should be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a chip embedded in a substrate to form a composite air bearing surface in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 2</figref> is a top view of a chip embedded in a substrate to form a composite air bearing surface in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 3</figref> is a front view of a chip embedded in a substrate to form a composite air bearing surface in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 4</figref> is a sectional view taken along the line <b>4</b>—<b>4</b> in <figref idref="DRAWINGS">FIG. 3</figref>, of a chip embedded in a substrate to form a composite air bearing surface in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 5</figref> is a perspective view of an apparatus for aligning and bonding a chip with a substrate in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 6</figref> is a cutaway perspective view of a portion of an apparatus for aligning and bonding a chip with a substrate in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 6A</figref> is another cutaway perspective view of a portion of an apparatus for aligning and bonding a chip with a substrate in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 7</figref> is a bottom perspective view of a pick-up chuck of an apparatus for aligning and bonding a chip with a substrate, in accordance with an example of the invention.

<figref idref="DRAWINGS">FIG. 8</figref> is a side view of an adhesive dispenser attached to a base in accordance with an example of the invention.

<figref idref="DRAWINGS">FIGS. 9A and 9B</figref> are a flowchart of an operational sequence for embedding a chip in a substrate to form a composite air bearing surface in accordance with an example of the invention.

DETAILED DESCRIPTION

The nature, objectives, and advantages of the invention will become more apparent to those skilled in the art after considering the following detailed description in connection with the accompanying drawings.

I. Hardware Components and Interconnections

A. Tape Head Module

One aspect of the invention concerns a read/write module that has a composite air bearing surface that may be used, for example, in a tape head. As an example, the read/write module may be embodied by the module <b>100</b> shown in <figref idref="DRAWINGS">FIGS. 1–4</figref>. <figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of the module <b>100</b>, <figref idref="DRAWINGS">FIG. 2</figref> is a top view of the module <b>100</b>, <figref idref="DRAWINGS">FIG. 3</figref> is a front view of the module <b>100</b>, and <figref idref="DRAWINGS">FIG. 4</figref> is a sectional view of the module <b>100</b> taken along the line <b>4</b>—<b>4</b> in <figref idref="DRAWINGS">FIG. 3</figref>. The module <b>100</b> includes a composite air bearing surface <b>102</b>, a substrate <b>104</b>, a chip <b>106</b>, and a closure <b>108</b>. As an example, the substrate <b>104</b> and chip <b>106</b> may both be made of N58 AlTiC. The substrate <b>104</b> has a substrate air bearing surface <b>110</b> that has a first portion <b>112</b> and a second portion <b>114</b>. The substrate <b>104</b> also has a bottom <b>116</b>, a front <b>118</b>, a back <b>120</b>, a first side <b>122</b>, a second side <b>124</b>, and a chip receiving slot <b>126</b>. The chip <b>106</b> has a chip air bearing surface <b>128</b>, a bottom surface <b>130</b> (shown most clearly in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>), a front <b>132</b> of the chip <b>106</b>, a front <b>133</b> of the chip air bearing surface <b>128</b>, a back <b>134</b>, a first side <b>136</b>, and a second side <b>138</b>. The substrate air bearing surface <b>110</b> and the chip air bearing surface <b>128</b> together form the composite air bearing surface <b>102</b>. The chip <b>106</b> also has a first front corner <b>139</b><i>a </i>(shown most clearly in <figref idref="DRAWINGS">FIG. 2</figref>), a second front corner <b>139</b><i>b</i>, a first back corner <b>139</b><i>c</i>, and a second back corner <b>139</b><i>d</i>. The chip <b>106</b> also has active elements <b>140</b> (shown most clearly in <figref idref="DRAWINGS">FIGS. 2 and 4</figref>) that are located proximate to the front <b>132</b> of the chip <b>106</b>. Accordingly, the chip <b>106</b> may be referred to as an active element chip. The active elements <b>140</b> in the chip <b>106</b> may include, for example, eight readers, eight writers, and two servos. However, the active elements <b>140</b> could include larger or smaller numbers of readers, writers, and/or servos. The readers may be, for example, magneto resistive (MR) elements. The readers may also be called sensors. The closure <b>108</b> has a closure air bearing surface <b>141</b>, a front <b>142</b>, and a back <b>144</b>, and the back <b>144</b> of the closure <b>108</b> is attached to the front <b>132</b> of the chip <b>106</b>. Electrical leads (not shown) for the active elements <b>140</b> may be coupled to pads <b>145</b> on the front <b>132</b> of the chip <b>106</b> beneath the closure <b>108</b>. In order to provide connections to the active elements <b>140</b>, the number of pads <b>145</b> provided on the chip <b>106</b> may be greater than the number of pads <b>145</b> shown in <figref idref="DRAWINGS">FIG. 3</figref>.

The length of the substrate <b>104</b> from the first side <b>122</b> of the substrate <b>104</b> to the second side <b>124</b> of the substrate <b>104</b> may be, for example, about 22.5 mm. The height of the substrate from the bottom <b>116</b> of the substrate <b>104</b> to the air bearing surface <b>110</b> of the substrate <b>104</b> may be, for example, about 2.5 mm. The distance from the front <b>118</b> to the back <b>120</b> of the substrate <b>104</b> (the width of the substrate <b>104</b>) may be, for example, about 2.0 mm. The substrate <b>104</b> may also include a first front protrusion <b>146</b> that has a face <b>148</b>, and a second front protrusion <b>150</b> that has a face <b>152</b>. The distance from the face <b>148</b> of the first front protrusion <b>146</b> and the face <b>152</b> of the second front protrusion <b>150</b> to the back <b>120</b> of the substrate <b>104</b> may be, for example, about 2.75 mm. The air bearing surface <b>110</b> of the substrate <b>104</b> has a back edge <b>154</b>. The distance from the front <b>118</b> of the substrate <b>104</b> to the back edge <b>154</b> of the air bearing surface <b>110</b> on the substrate <b>104</b> may be, for example, about 0.63 mm, and in another example could be, for example about 0.80 mm. However, other distances could be utilized.

The tape used with the module <b>100</b> may, as an example, be about 1.27 cm (0.5 inch) wide. However, different tape widths could be used, and, if necessary, the width of the substrate <b>104</b> could be adjusted to accommodate different tape widths.

The length of the chip <b>106</b> from the first side <b>136</b> of the chip <b>106</b> to the second side <b>138</b> of the chip <b>106</b> may be, for example, about 6.8 mm. The thickness of the chip <b>106</b> from the bottom surface <b>130</b> of the chip <b>106</b> to the air bearing surface <b>128</b> of the chip <b>106</b> may be, for example, about 550±15 μm. The distance from the front <b>132</b> to the back <b>134</b> of the chip <b>106</b> (the width of the chip <b>106</b>) may be, for example, about 2.0 mm. Thus, the bonding area on the bottom surface <b>130</b> of the chip <b>106</b> may be about 6.8 mm by about 2.0 mm. The air bearing surface <b>128</b> of the chip <b>106</b> has a back edge <b>156</b>. The distance from the front <b>132</b> of the chip <b>106</b> to the back edge <b>156</b> of the air bearing surface <b>128</b> on the chip <b>106</b> may be, for example, about 0.63 mm, and in another example could be, for example 0.80 mm. However, other distances could be utilized. The distance from the front <b>142</b> to the back <b>144</b> of the closure <b>108</b> may be, for example, about 0.225 mm.

In the module <b>100</b> shown in the illustrated example, the chip <b>106</b> has a tail surface <b>157</b> that may be substantially parallel to the air bearing surface <b>128</b> of the chip <b>106</b> and the air bearing surface <b>110</b> of the substrate <b>104</b>. Similarly, the substrate <b>104</b> has a tail surface <b>158</b> that has a first portion <b>159</b> adjoining a rear portion of the first side <b>166</b> of the chip receiving slot <b>126</b>, and a second portion <b>160</b> adjoining a rear portion of the second side <b>168</b> of the chip receiving slot <b>126</b>. The tail surface <b>158</b> of the substrate <b>104</b> is substantially coplanar with the tail surface <b>157</b> of the chip <b>106</b>. The tail surfaces <b>157</b>, <b>158</b> do not have to be parallel to the air bearing surfaces <b>128</b>, <b>110</b>. The tail surface <b>157</b> of the chip <b>106</b> is located between the air bearing surface <b>128</b> of the chip <b>106</b> and the back <b>134</b> of the chip <b>106</b>, and is located in a plane positioned between the air bearing surface <b>128</b> of the chip <b>106</b> and the bottom surface <b>130</b> of the chip <b>106</b>. Similarly, the tail surface <b>158</b> of the substrate is located between the air bearing surface <b>110</b> of the substrate <b>104</b> and the back <b>120</b> of the substrate <b>104</b>. The tail surface <b>157</b> of the chip <b>106</b> and tail surface <b>158</b> of the substrate <b>104</b> may be formed by a taperless grind operation, discussed below, in which a substantially rectangular rear portion of the composite air bearing surface <b>102</b> is removed. The chip tail surface <b>157</b> and the substrate tail surface <b>158</b> may be, for example, about 0.18 mm from the plane defined by the air bearing surface <b>128</b> of the chip <b>106</b>. The distance from the back <b>134</b> of the chip <b>106</b> to a front edge <b>161</b> of the tail surface <b>157</b> of the chip <b>106</b>, and from the back <b>120</b> of the substrate <b>104</b> to a front edge <b>162</b> of the tail surface <b>158</b> of the substrate <b>104</b>, may be, for example, about 1.75 mm.

As shown most clearly in <figref idref="DRAWINGS">FIGS. 3–4</figref>, the chip receiving slot <b>126</b> in the substrate <b>104</b> has a front <b>163</b> at the front <b>118</b> of the substrate <b>104</b>, a back <b>164</b> at the back <b>120</b> of the substrate <b>104</b>, a first side <b>166</b>, a second side <b>168</b>, and a bonding surface <b>170</b>. The chip receiving slot <b>126</b> also has a first side trough <b>172</b> proximate to the first side <b>166</b> of the chip receiving slot <b>126</b>, and a second side trough <b>174</b> proximate to the second side <b>168</b> of the chip receiving slot <b>126</b>. The first side trough <b>172</b> has a bottom <b>176</b>, and the second side trough <b>174</b> has a bottom <b>178</b>. The depth of the chip receiving slot <b>126</b> is chosen so that the air bearing surface <b>128</b> of the chip <b>106</b> will be substantially aligned with the air bearing surface <b>110</b> of the substrate <b>104</b> over the temperature and humidity ranges to which the module <b>100</b> is likely to be exposed, despite expansion or contraction of the adhesive and tolerance variations in the thickness of the chip <b>106</b>. In the illustrated example, when the chip <b>106</b> is placed in the chip receiving slot <b>126</b>, the back <b>134</b> of the chip <b>106</b> is aligned with the back <b>164</b> of the chip receiving slot <b>126</b>. However, the chip <b>106</b> does not have to extend to the back <b>164</b> of the chip receiving slot <b>126</b>. The length of the chip receiving slot <b>126</b> from the first side <b>166</b> of the chip receiving slot to the second side <b>168</b> of the chip receiving slot <b>126</b> may be, for example about 7.0 mm, and, for example, is centered along the 22.5 mm length of the substrate <b>104</b>. The width of the chip receiving slot <b>126</b> from the front <b>163</b> of the chip receiving slot <b>126</b> to the back <b>164</b> of the chip receiving slot <b>126</b> may be, for example, about 2.0 mm. The distance from the air bearing surface <b>110</b> of the substrate <b>104</b> to the bonding surface <b>170</b> of the chip receiving slot <b>126</b> may be, for example, about 580±15 μm. The distance from the air bearing surface <b>110</b> of the substrate <b>104</b> to the bottom <b>176</b> of the first side trough <b>172</b> and to the bottom <b>178</b> of the second side trough <b>174</b> may be, for example about 0.65 mm.

The first portion <b>112</b> of the substrate <b>104</b> air bearing surface <b>110</b> adjoins the first side <b>166</b> of the chip receiving slot <b>126</b>, and the second portion <b>114</b> of the substrate <b>104</b> air bearing surface <b>110</b> adjoins the second side <b>168</b> of the chip receiving slot <b>126</b>. The chip <b>106</b> is inserted in the chip receiving slot <b>126</b> in the substrate <b>104</b> with the air bearing surface <b>128</b> of the chip <b>106</b> substantially aligned with the air bearing surface <b>110</b> of the substrate <b>104</b>, and with the back <b>134</b> of the chip <b>106</b> substantially aligned with the back <b>120</b> of the substrate <b>104</b>.

An adhesive layer <b>180</b> (shown most clearly in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>) is attached to the bonding surface <b>170</b> of the chip receiving slot <b>126</b> and to the bottom surface <b>130</b> of the chip <b>106</b>. As an example, the adhesive layer <b>180</b> may be U.V. cured. Additionally, the adhesive layer <b>180</b> fills at least a portion of the fist side trough <b>172</b> and/or the second side trough <b>174</b>.

B. Apparatus for Aligning and Bonding a Chip with a Substrate

Another aspect of the invention concerns an apparatus for aligning and bonding a chip <b>106</b> with a substrate <b>104</b> to form a composite air bearing surface <b>102</b>. The apparatus may be called a bonding apparatus, a bonding machine, or a fixture. As an example, the apparatus may be embodied by the apparatus <b>500</b> shown in <figref idref="DRAWINGS">FIG. 5</figref>. <figref idref="DRAWINGS">FIG. 5</figref> is a perspective view of the apparatus <b>500</b>, <figref idref="DRAWINGS">FIGS. 6 and 6A</figref> are cutaway perspective views of portions of the apparatus <b>500</b>, and <figref idref="DRAWINGS">FIG. 7</figref> is a bottom perspective view of a pick-up chuck <b>502</b> of the apparatus <b>500</b>. The apparatus <b>500</b> includes a housing <b>504</b> that has a substrate seat <b>506</b> (shown most clearly in <figref idref="DRAWINGS">FIG. 6A</figref>). In <figref idref="DRAWINGS">FIG. 6</figref> the substrate <b>104</b> is shown in the substrate seat <b>506</b>, and in <figref idref="DRAWINGS">FIG. 6A</figref> the substrate seat <b>506</b> is shown without the substrate <b>104</b>. The substrate seat <b>506</b> has back surfaces <b>508</b><i>a</i>, <b>508</b><i>b</i>, <b>508</b><i>c</i>, <b>508</b><i>d </i>(which can be called datums or stops), a bottom <b>510</b>, a front edge <b>511</b>, and a side <b>512</b> (all shown most clearly in <figref idref="DRAWINGS">FIG. 6A</figref>). In alternative embodiments, the substrate seat <b>506</b> could have one, two, three, or five or more back surfaces. The apparatus <b>500</b> may also include a substrate front clamp <b>514</b> (shown most clearly in <figref idref="DRAWINGS">FIG. 6</figref>) slidably mounted on the housing <b>504</b> for selectively holding the substrate <b>104</b> in the substrate seat <b>506</b>, and a substrate side clamp <b>516</b> (shown most clearly in <figref idref="DRAWINGS">FIGS. 6 and 6A</figref>) slidably mounted on the housing for selectively holding the substrate <b>104</b> in the substrate seat <b>506</b>. The apparatus <b>500</b> also includes an alignment arm <b>518</b> (shown in <figref idref="DRAWINGS">FIGS. 5 and 6</figref>) slidably attached to the housing <b>504</b>. The pick-up chuck <b>502</b> (shown most clearly in <figref idref="DRAWINGS">FIGS. 5 and 7</figref>) is slidably attached to the alignment arm <b>518</b>. The pick-up chuck <b>502</b> has bottom surface <b>520</b> (shown in <figref idref="DRAWINGS">FIG. 7</figref>). A first alignment foot <b>522</b>, and a second alignment foot <b>524</b> (shown in <figref idref="DRAWINGS">FIG. 7</figref>), are attached to the pick-up chuck <b>502</b>, and protrude from the bottom surface <b>520</b> of the pick-up chuck <b>502</b>. The first alignment foot <b>522</b> has a bottom surface <b>526</b>, and the second alignment foot <b>524</b> has a bottom surface <b>528</b>. In alternative embodiments, more than two alignment feet could be used. For example, four alignment feet could be used.

A first fiber optic U.V. light guide <b>530</b> (shown most clearly in <figref idref="DRAWINGS">FIG. 5</figref>) is attached to the housing <b>504</b>. A first end <b>532</b> of the first fiber optic U.V. light guide <b>530</b> is located proximate to the front edge <b>511</b> of the substrate seat <b>506</b> about 2 mm above the bottom <b>510</b> of the substrate seat <b>506</b>. A second end <b>534</b> of the first fiber optic U.V. light guide <b>530</b> is configured for coupling to a U.V. light source (not shown). Similarly, a second fiber optic U.V. light guide <b>536</b> may also be attached to the housing <b>504</b>. A first end <b>538</b> of the second fiber optic U.V. light guide <b>536</b> is located proximate to the front edge <b>511</b> of the substrate seat <b>506</b> about 2 mm above the bottom <b>510</b> of the substrate seat <b>506</b>, and a second end <b>540</b> of the second fiber optic U.V. light guide <b>536</b> is configured for coupling to the U.V. light source. A third fiber optic U.V. light guide <b>542</b> may also be attached to the housing <b>504</b>. A first end <b>544</b> of the third fiber optic U.V. light guide <b>542</b> is located proximate to the back surfaces <b>508</b><i>b</i>, <b>508</b><i>c </i>of the substrate seat <b>506</b>, and a second end <b>546</b> of the third fiber optic U.V. light guide <b>542</b> is configured for coupling to the U.V. light source. The U.V. light guides may also be called wands.

The bottom surface <b>520</b> (shown in <figref idref="DRAWINGS">FIG. 7</figref>) of the pick-up chuck <b>502</b> may have a hole <b>548</b> for coupling to a vacuum source (not shown) for holding the air bearing surface <b>128</b> of the chip <b>106</b> against the bottom surface <b>520</b> of the pick-up chuck <b>502</b>. Additionally, a chip seat <b>550</b> (shown most clearly in <figref idref="DRAWINGS">FIG. 6</figref>) that has a slot <b>552</b> for receiving the chip <b>106</b>, may be formed in the housing <b>504</b>, for aligning the chip <b>106</b> in a y direction (which may also be referred to as a first direction) and for holding the chip <b>106</b> before it is picked up by the pick-up chuck <b>502</b>. The chip seat <b>550</b> may have a hole <b>554</b> for coupling to the vacuum source, for holding the chip <b>106</b> on the chip seat <b>550</b>.

The apparatus <b>500</b> may also include an adhesive dispenser <b>556</b> and a base <b>557</b>, which are shown in <figref idref="DRAWINGS">FIG. 8</figref>. The base <b>557</b> may be attached to the housing <b>504</b>. The adhesive dispenser <b>556</b> has a hole <b>558</b> (which may also be called an opening), for dispensing adhesive. The adhesive dispenser <b>556</b> is attached to a first dispenser holder arm <b>559</b>, and a second dispenser holder arm <b>560</b>, which are attached to a dispenser stand <b>561</b>. The adhesive dispenser <b>556</b> may be selectively coupled to an air pressure source (not shown) for pushing the adhesive out of the hole <b>558</b> of the adhesive dispenser <b>556</b>. As an example, an air tube (not shown) may be coupled to the adhesive dispenser for supplying air pressure from an air pressure source for pushing the adhesive out of the hole <b>558</b>. The adhesive dispenser may <b>556</b> be attached to actuators (not shown) for moving the hole <b>558</b> in the adhesive dispenser <b>556</b> over the chip receiving slot <b>126</b> in the substrate <b>104</b> to deposit adhesive in the chip receiving slot <b>126</b>. As an example, three electrical actuators may be attached to the dispenser stand <b>561</b> for moving the adhesive dispenser <b>556</b> in x, y, and z directions. The x direction may be referred to as a second direction, the y direction may be referred to as a first direction, and the z direction may be referred to as a third direction.

Movement of the alignment arm <b>518</b> may be accomplished, for example, by coupling an air pressure source to a cylinder (not shown) attached to, or formed in, the alignment arm <b>518</b>. As an example, a tube may be used to couple air from an air compressor to the cylinder. Air pressure may be applied to one side of the cylinder to move the cylinder and the alignment arm <b>518</b> in a first direction, and may be applied to an opposite side of the cylinder to move the cylinder and the alignment arm <b>518</b> in an opposite direction. The substrate front clamp <b>514</b> and the substrate side clamp <b>516</b> may, for example, be moved in a similar fashion with air pressure. Bearings (not shown) may be utilized to facilitate smooth movement of the alignment arm <b>518</b>. Vertical movement of the pick-up chuck <b>502</b> may be accomplished, for example, with an air bladder <b>562</b> coupled to the pick-up chuck <b>502</b> with a pivot arm <b>564</b>. The air bladder <b>562</b> may be coupled to an air pressure source (not shown) for inflating and deflating the air bladder <b>562</b>. For example, the pick-up chuck <b>502</b> may be moved downward by putting air into the air bladder <b>562</b>, and may be moved upward by removing air from the air bladder <b>562</b>. Air lines, valves, switches, manifolds, and pressure regulators (not shown), may be utilized to couple the air pressure source (or air pressure sources) to the alignment arm <b>518</b>, the bladder <b>562</b>, the substrate front clamp <b>514</b>, the substrate side clamp <b>517</b>, the hole <b>548</b> in the bottom surface <b>520</b> of the pick-up chuck <b>502</b>, the hole <b>554</b> in the chip seat <b>550</b>, and to the adhesive dispenser <b>556</b>. The air pressure source may, for example, provide positive air pressure and/or negative air pressure (to create a vacuum source). A processor, for example a portable computer, may be coupled to the air pressure source, valves, and actuators for controlling operation of the apparatus <b>500</b>. Alternatively, electric actuators could be used to move the alignment arm <b>518</b>, the pick-up chuck <b>502</b>, the substrate front clamp <b>514</b>, and the substrate side clamp <b>516</b>.

Alignment of the plane of the air bearing surface <b>128</b> of the chip <b>106</b> with the plane of the air bearing surface <b>110</b> of the substrate <b>104</b> is accomplished mechanically with the apparatus <b>500</b>, by having a portion of the apparatus <b>500</b> touch the air bearing surface <b>110</b> of the substrate <b>104</b> at specified locations to stop vertical motion of the chip <b>106</b>, as is discussed below. To maintain optimal performance, the fixture <b>500</b> could be periodically realigned, and a mechanized (or manual) fixture cleaning process could be used to clean the fixture <b>500</b> between uses.

II. Operation

In addition to the various hardware embodiments described above, another aspect of the invention concerns a method for embedding a chip in a substrate, to form a composite air bearing surface, which may be used in a tape head. Embedding the chip in the substrate may also be referred to as merging the chip with the substrate.

Overall Sequence of Operation

For ease of explanation, but without any intended limitation, the method aspect of the invention is described with reference to the read/write module <b>100</b> and the apparatus <b>500</b> described above. An example of the method aspect of the present invention is illustrated in <figref idref="DRAWINGS">FIGS. 9A and 9B</figref>, which show a sequence <b>900</b> for a method for embedding a chip <b>106</b> in a substrate <b>104</b> to form a composite air bearing surface <b>102</b>.

The sequence <b>900</b>, may begin with the operation <b>902</b> of attaching a closure <b>108</b> to the chip <b>106</b>, adjacent the active elements <b>140</b> in the chip <b>106</b>. The closure <b>108</b> is attached to the front <b>132</b> of the chip. However, the closure <b>108</b>, which is included for example to reduce tape wear on the active elements <b>140</b>, is not required. The sequence <b>900</b> may also include the operation <b>904</b> of lapping the chip <b>106</b> to form the air bearing surface <b>128</b> on the chip <b>106</b>, prior to performing the aligning operation <b>914</b> discussed below. The sequence <b>900</b> may further include lapping the bottom surface <b>130</b> of the chip <b>106</b>, in operation <b>906</b>, to produce sufficient surface roughness on the bottom surface <b>130</b> to increase adhesive reliability and bond strength (discussed below). Operation <b>908</b> may also be performed, which comprises grinding the chip receiving slot <b>126</b> in the substrate <b>104</b>, prior to the operation <b>916</b> of depositing adhesive in the chip receiving slot <b>126</b>, which is discussed below. The sequence <b>900</b> may also include the operation <b>910</b> of lapping the substrate <b>104</b> to form the air bearing surface <b>110</b> on the substrate <b>104</b>, also prior to the operation <b>916</b> of depositing adhesive in the chip receiving slot <b>126</b>, discussed below. As an example, the air bearing surface <b>110</b> of the substrate <b>104</b> may be lapped after the chip receiving slot <b>126</b> is ground in the substrate <b>104</b>, to avoid distortion of the air bearing surface <b>110</b> that could result if the chip receiving slot <b>126</b> is ground in the substrate <b>104</b> after the air bearing surface <b>110</b> of the substrate <b>104</b> is lapped. In one example the air bearing surface <b>110</b> of the substrate <b>104</b> is polished to the same Ra as the air bearing surface <b>128</b> of the chip <b>106</b>, which may be, for example about 50 Å Ra.

In operation <b>912</b>, the substrate <b>104</b> is secured in a fixed position. As an <b>25</b> example, the substrate <b>104</b> may be secured in the substrate seat <b>506</b> by pressing the substrate front clamp <b>514</b> and/or the substrate side clamp <b>516</b> against the substrate, thereby causing the substrate <b>104</b> to be pushed against the back surfaces <b>508</b><i>a</i>, <b>508</b><i>b</i>, <b>508</b><i>c</i>, <b>508</b><i>d </i>and the side <b>512</b> of the substrate seat <b>506</b>. In some embodiments there may be a hole (not shown) in the bottom <b>510</b> of the substrate seat <b>506</b>, and air may be evacuated from the hole to hold the bottom <b>116</b> of the substrate <b>104</b> against the bottom <b>510</b> of the substrate seat <b>506</b>. A vacuum source could be coupled to the hole to evacuate air from the hole.

The sequence <b>900</b> also includes operation <b>914</b>, which comprises aligning the chip <b>106</b> in a y direction (also called the first direction) with the chip receiving slot <b>126</b> in the substrate <b>104</b>. The operation <b>914</b> of aligning the chip <b>106</b> in the y direction may be performed before or after the operation <b>916</b> of depositing adhesive (discussed below). The chip <b>106</b> is aligned in the y direction with the chip receiving slot <b>126</b> when the distance from the first side <b>136</b> of the chip <b>106</b> to the first side <b>166</b> of the chip receiving slot <b>126</b>, and the distance from the second side <b>138</b> of the chip <b>106</b> to the second side <b>168</b> of the chip receiving slot, are about the same. Because the distance from the first side <b>136</b> to the second side <b>138</b> of the chip <b>106</b> is slightly less than the distance from the first side <b>166</b> to the second side <b>168</b> of the chip receiving slot <b>126</b>, the chip <b>106</b> will fit into the chip receiving slot <b>126</b> when the chip <b>106</b> is later pushed into adhesive in the chip receiving slot <b>126</b> (in operation <b>922</b> discussed below). As an example, the chip <b>106</b> may be aligned in the y direction by placing the chip <b>106</b> in the slot <b>552</b> in the chip seat <b>550</b>. The slot <b>552</b> is sized and positioned so that when the chip <b>106</b> is placed in the slot <b>552</b>, the first side <b>136</b> of the chip <b>106</b> is about 0.1 mm towards the center of the chip receiving slot <b>126</b> in the y direction from the first side <b>166</b> of the chip receiving slot <b>126</b>, and the second side <b>138</b> of the chip <b>106</b> is about 0.1 mm towards the center of the chip receiving slot <b>126</b> in the y direction from the second side <b>168</b> of the chip receiving slot <b>126</b>. The chip <b>106</b> may be held in position in the slot <b>552</b> by coupling the hole <b>554</b> in the chip seat <b>550</b> to a vacuum source to evacuate air from the hole <b>554</b> in the chip seat <b>550</b>.

In operation <b>916</b>, adhesive is deposited in the chip receiving slot <b>126</b> in the substrate <b>104</b>. Operation <b>916</b> may be accomplished by applying pressure to adhesive in the adhesive dispenser <b>556</b> to cause adhesive to flow from the hole <b>558</b> in the adhesive dispenser <b>556</b>, and by moving the hole <b>558</b> in the adhesive dispenser <b>556</b> over the chip receiving slot <b>126</b> while adhesive flows from the hole <b>556</b>. In one example the adhesive is deposited at least 5 microns thick on the bonding surface <b>170</b> of the chip receiving slot <b>126</b>. However, smaller or larger adhesive thicknesses could be used. In some embodiments the adhesive may be a U.V. curable cyanoacrylate. However, the adhesive does not have to be U.V. curable. Also, the adhesive does not have to be a cyanoacrylate. In one example the adhesive may be part number 4303 manufactured by Loctite Corporation. Loctite 4303 does not require pressing together the parts that are to be bonded. Other adhesives available from Loctite Corporation, for example model numbers 4302 or 4205, or adhesives available from other sources, could also possibly be used. In an alternative embodiment, a U.V. curable adhesive could be placed only near the four corners of the bonding surface <b>170</b> of the chip receiving slot <b>126</b> to hold the chip <b>106</b> in place, and then later a stronger adhesive could be added between the bottom surface <b>130</b> of the chip <b>106</b> and the bonding surface <b>170</b> of the chip receiving slot <b>126</b> to increase the bond strength and reliability.

The humidity characteristics of the adhesive affect the functionality and reliability of the module <b>100</b>. Adhesives generally shrink when cured, and swell when subjected to humidity. The amount of adhesive expansion due to humidity is greater if there is more adhesive thickness. The adsorption of moisture with exposure to elevated temperatures and humidities is low for Loctite 4303, and is between 0.25% and 0.78% by weight. Loctite 4303 was measured to exhibit low humidity expansion of 0.035 mm/mm at 35° C., 95% R.H. (relative humidity). The adsorbed water causes expansion of the adhesive, which increases the protrusion of the air bearing surface <b>128</b> of the chip <b>106</b>, by 3.5±0.4% of the adhesive thickness. For a 60 μm thick adhesive, the expansion would be 2.1±0.2 μm. Adhesive expansion can also degrade the cohesive strength of the adhesive. Additionally, moisture may diffuse along the interface between the adhesive and the substrate <b>104</b> and/or the chip <b>106</b>, potentially degrading the adhesive bond strength. The humidity properties of the adhesive are of interest because the module <b>100</b> is subjected to water if the taperless grind operation <b>936</b>, discussed below, is performed. Furthermore, tape heads used in the data storage industry are also exposed to variations in ambient environmental conditions, which include humidity and temperature variations.

The strength of the bond between the substrate <b>104</b> and the chip <b>106</b> is another important characteristic that affects the functionality and reliability of the module <b>100</b>. The break force of the bond between the substrate <b>104</b> and the chip <b>106</b> ideally should be sufficiently large to prevent (or minimize) movement or degradation of the bond during processing of the module <b>100</b> and when the module <b>100</b> is exposed to environmental conditions over the life of the module <b>100</b>, for example humidity and temperature variations. It is desirable to have a tight distribution of the break force for modules <b>100</b> produced in accordance with the invention. The break force may be measured, for example, by holding the substrate <b>104</b> fixed while applying a pseudo-shear force to the chip <b>106</b> until the bond breaks.

The bottom surface <b>130</b> of the chip <b>106</b> and the bonding surface <b>170</b> of the chip insertion slot <b>126</b> may be made sufficiently rough to improve the bond strength and humidity properties of the bond. Generally, the bottom surface <b>130</b> of the chip <b>106</b> is lapped to make as rough of a surface as can be produced without causing excessive wear on the chip <b>106</b> or excessive bowing of the chip air bearing surface <b>128</b>. The bond strength may be improved by lapping the bottom surface <b>130</b> of the chip <b>106</b>, for example, with a 6 μm diamond paste to produce a surface roughness between about 70 Å Ra and about 205 Å Ra, with an average of about 130 Å Ra. As another example, the bond strength may also be improved by lapping the bonding surface <b>170</b> of the chip insertion slot <b>126</b> to yield a surface roughness of N<b>5</b>–N<b>6</b>, which is 0.8 μm Ra to 1.6 μm Ra.

The sequence <b>900</b> may also include the operation <b>918</b> of evacuating air from the hole <b>548</b> in the bottom surface <b>520</b> of the pick-up chuck <b>502</b>, to pick up the chip <b>106</b> and hold the air bearing surface <b>128</b> of the chip <b>106</b> against the bottom surface <b>520</b> of the pick-up chuck <b>502</b>. The chip <b>106</b> may be picked up by the pick-up chuck <b>502</b> to facilitate moving the chip <b>106</b> by moving the alignment arm <b>518</b>. The alignment arm <b>518</b> may be moved in an x direction (also called the second direction) to align the chip <b>106</b> in the x direction with the chip receiving slot <b>126</b> in the substrate <b>104</b>, in operation <b>920</b> (discussed below). The chip <b>106</b> may be held against the pick-up chuck until the U.V. curing (discussed below) is completed. To evacuate air from the hole <b>548</b>, a vacuum source (not shown) may be coupled to the hole <b>548</b> with a tube (not shown). The vacuum source may be the same vacuum source, or a different vacuum source than the vacuum source used for evacuating air from the hole <b>554</b> in the chip seat <b>550</b>. To facilitate picking up the chip <b>106</b> with the pick-up chuck <b>502</b>, the vacuum source may be decoupled from the hole <b>554</b> in the chip seat <b>550</b> prior to when the chip <b>106</b> is picked up by the pick-up chuck <b>502</b>. The chip <b>106</b> remains aligned in the y direction when it is picked up by the pick-up chuck <b>502</b> on the alignment arm <b>518</b>.

In operation <b>920</b> the chip <b>106</b> is aligned in the x direction with the chip receiving slot <b>126</b> in the substrate <b>104</b>. The chip <b>106</b> may be aligned in the x direction with the chip receiving slot <b>126</b> in the substrate <b>104</b> by substantially aligning the back <b>134</b> of chip <b>106</b> with the back <b>120</b> of the substrate <b>104</b>, or, by substantially aligning the front <b>133</b> of the air bearing surface <b>128</b> of the chip <b>106</b> with the front <b>163</b> of the chip receiving slot <b>126</b>. For example, the chip <b>106</b> may be aligned with the substrate <b>104</b> in the x direction by picking up the chip <b>106</b> with the pick-up chuck <b>502</b>, and then moving the pick-up chuck <b>502</b> and the chip <b>106</b> over the substrate <b>104</b> until the back <b>134</b> of the chip <b>106</b> touches the back surfaces <b>508</b><i>b</i>, <b>508</b><i>c </i>of the substrate seat <b>506</b>. Because the substrate <b>104</b> has been secured to the substrate seat <b>506</b> in operation <b>912</b>, the back <b>120</b> of the substrate <b>104</b> also is touching the back surfaces <b>508</b><i>b</i>, <b>508</b><i>c </i>(and back surfaces <b>508</b><i>a</i>, <b>508</b><i>d</i>) of the substrate seat <b>506</b>.

The sequence <b>900</b> also includes the operation <b>922</b> of pushing the chip <b>106</b> into the adhesive in the chip receiving slot <b>126</b> of the substrate <b>104</b>. The pushing operation <b>922</b> may be accomplished by lowering the pick-up chuck <b>502</b>, while holding the chip <b>106</b> on the bottom surface <b>520</b> of the pick-up chuck <b>502</b>, with the air bearing surface <b>128</b> of the chip <b>106</b> substantially parallel with the air bearing surface <b>110</b> of the substrate <b>104</b>. As an example, in the pushing operation <b>922</b> the chip <b>106</b> is pushed into the adhesive only in the negative z direction. The pushing operation <b>922</b> may also include pushing a portion of the adhesive into a plurality of troughs <b>172</b>, <b>174</b> in the chip receiving slot <b>126</b> in the substrate <b>104</b>. The adhesive may be pushed into the plurality of troughs <b>172</b>, <b>174</b> by the bottom surface <b>130</b> of the chip <b>106</b> as the chip <b>106</b> is pushed into the adhesive. The plurality of troughs <b>172</b>, <b>174</b> are provided so that excessive adhesive will flow into the troughs <b>172</b>, <b>174</b> rather than on to the composite air bearing surface <b>102</b>.

The sequence <b>900</b> further includes the operation <b>924</b> of detecting when the air bearing surface <b>128</b> of the chip <b>106</b> is substantially at a desired protrusion in the z direction in relation to the air bearing surface <b>110</b> of the substrate <b>104</b>. The z direction may also be referred to as the third direction. The z direction is perpendicular to the air bearing surface <b>110</b> of the substrate <b>104</b>, and the desired protrusion of the air bearing surface <b>128</b> of the chip <b>106</b> can be a negative, positive, or zero value with reference to the air bearing surface <b>110</b> of the substrate <b>104</b>. The detecting operation <b>924</b> may be accomplished by detecting when the bottom surface <b>526</b> of the first alignment foot <b>522</b> and the bottom surface <b>528</b> of the second alignment foot <b>524</b> contact the air bearing surface <b>110</b> of the substrate <b>104</b>. The air bearing surface <b>110</b> of the substrate <b>104</b> is used as a datum for determining when the air bearing surface <b>128</b> of the chip <b>106</b> is at the desired protrusion in the z direction. The distance that the first alignment foot <b>522</b> and the second alignment foot <b>524</b> extend from the bottom surface <b>520</b> of the pick-up chuck <b>502</b> is chosen so that the bottom surface <b>526</b> of the first alignment foot <b>522</b> and the bottom surface <b>528</b> of the second alignment foot <b>524</b> will contact the air bearing surface <b>110</b> of the substrate <b>104</b> when the air bearing surface <b>128</b> of the chip <b>106</b> is substantially at the desired protrusion in the z direction.

In operation <b>926</b>, responsive to detecting that the air bearing surface <b>128</b> of the chip <b>106</b> is substantially at the desired protrusion in the z direction in relation to the air bearing surface <b>110</b> of the substrate <b>104</b>, pushing the chip <b>106</b> into the adhesive is ceased. When the bottom surface <b>526</b> of the first alignment foot <b>522</b> and the bottom surface <b>528</b> of the second alignment foot <b>524</b> contact the air bearing surface <b>110</b> of the substrate <b>104</b>, the first alignment foot <b>522</b> and the second alignment foot <b>524</b> prevent the pick-up chuck <b>502</b> from lowering any further, thereby preventing the chip <b>106</b> from being pushed any further into the adhesive.

The protrusion of the air bearing surface <b>128</b> of the chip <b>106</b> in relation to the air bearing surface <b>110</b> of the substrate <b>104</b> is an important parameter concerning the performance and reliability of the module <b>100</b>. The initial protrusion is affected by the dimensional tolerances of the parts and the alignment of the chip <b>106</b> in the chip receiving slot <b>126</b> in the substrate <b>104</b>. Long term changes in the protrusion are caused primarily by temperature and humidity effects. In order to be able to read and write to tape in accordance with desired performance characteristics of the module <b>100</b>, the air bearing surface <b>128</b> of the chip <b>106</b> must be aligned with the air bearing surface <b>110</b> of the substrate <b>104</b> within a protrusion tolerance dictated by the desired performance characteristics of the module <b>100</b>. For example, there is generally no increase in read and write data error rates when the air bearing surface <b>128</b> of the chip <b>106</b> is aligned between about −4 μm and about +11 μm from the air bearing surface <b>110</b> of the substrate <b>104</b>. A negative number (such as −4 μm) indicates that the air bearing surface <b>128</b> of the chip <b>106</b> is lower than the air bearing surface <b>110</b> of the substrate <b>104</b>, and a positive number (such as +11 μm) indicates that the air bearing surface <b>128</b> of the chip <b>106</b> is higher than the air bearing surface <b>110</b> of the substrate <b>104</b>). Too low of a protrusion (wherein the air bearing surface <b>128</b> of the chip <b>106</b> is below the air bearing surface <b>110</b> of the substrate <b>104</b>) may result in a reduction and/or loss of servo, reader, and writer signals in the module due to Wallace spacing losses. Too high of a protrusion (wherein the air bearing surface <b>128</b> of the chip <b>106</b> is above the air bearing surface <b>110</b> of the substrate <b>104</b>) may cause excessive tape wear or damage or loss of servo signals. Generally, the air bearing surfaces <b>128</b>, <b>110</b> are substantially aligned when the air bearing surface <b>128</b> of the chip <b>106</b> is aligned in the z direction to within about −4 μm and about +11 μm from the air bearing surface <b>110</b> of the substrate <b>104</b>.

As an example, the air bearing surface <b>128</b> of the chip <b>106</b> is at the desired protrusion in the z direction when the air bearing surface <b>128</b> of the chip <b>106</b> is about 2 microns above the air bearing surface <b>110</b> of the substrate <b>104</b>. In this example, the air bearing surface <b>128</b> of the chip <b>106</b> is positioned 2 microns above the air bearing surface <b>110</b> of the substrate <b>104</b> to allow for possible lowering of the air bearing surface <b>128</b> of the chip <b>106</b> as the adhesive continues to cure after being initially cured with U.V. light. However, the desired protrusion of the air bearing surface <b>128</b> of the chip <b>106</b> in the z direction could be greater or lesser than 2 microns above the air bearing surface <b>110</b> of the substrate <b>104</b>, or below the air bearing surface <b>110</b> of the substrate <b>104</b>, or when the air bearing surfaces <b>128</b>, <b>110</b> are coplanar. Lapping of the combined air bearing surface <b>102</b>, which may be costly, is not required because the invention permits precisely positioning the chip <b>106</b> in the substrate <b>104</b> to produce the desired protrusion.

The protrusion of the air bearing surface <b>128</b> of the chip <b>106</b> in relation to the air bearing surface <b>110</b> of the substrate may be designated P<b>2</b> at the first front corner <b>139</b><i>a </i>(shown in <figref idref="DRAWINGS">FIG. 2</figref>) of the chip <b>106</b>, may be designated P<b>3</b> at the second front corner <b>139</b><i>b </i>of the chip <b>106</b>, may be designed P<b>1</b> at the first back corner <b>139</b><i>c </i>of the chip <b>106</b>, and may be designated P<b>4</b> at the second back corner <b>139</b><i>d </i>of the chip <b>106</b>. The protrusions P<b>2</b> and P<b>3</b> at the front corners <b>139</b><i>a–b</i>, are more important than the protrusions P<b>1</b> and P<b>4</b> at the back corners <b>139</b><i>c–d</i>, because the back corners <b>139</b><i>c–d </i>may later be removed from the composite air bearing surface <b>102</b> by a taperless grind operation (discussed below). If desired, a laser interferometer (which, for example, may be obtained from Zygo Corporation) may be used to measure protrusion tolerances. However, it is not necessary to measure tolerances when the air bearing surface <b>110</b> of the substrate <b>104</b> is used as a datum (reference surface) for detecting when the air bearing surface <b>128</b> of the chip <b>106</b> is at the desired protrusion in the z direction, because the desired protrusion exists when the first alignment foot <b>522</b> and the second alignment foot <b>524</b> contact the air bearing surface <b>110</b> of the substrate <b>104</b>. Using the datum may be quicker than individually measuring the protrusions P<b>1</b>, P<b>2</b>, P<b>3</b>, and P<b>4</b>, and adjusting the position of the chip <b>106</b>.

The sequence <b>900</b> may also include operation <b>928</b>, which comprises holding the chip <b>106</b>, with the air bearing surface <b>128</b> of the chip <b>106</b> substantially at the desired protrusion in the z direction in relation to the air bearing surface <b>110</b> of the substrate <b>104</b>, and with the chip <b>106</b> substantially aligned in the x and y directions with the chip receiving slot <b>126</b> in the substrate <b>104</b>. Due to the orientation of the bottom surface <b>520</b> of the pick-up chuck <b>502</b>, during the holding operation <b>928</b> the air bearing surface <b>128</b> of the chip <b>106</b> is substantially parallel with the air bearing surface <b>110</b> of the substrate <b>104</b>. In operation <b>930</b> the adhesive is cured to bond the bottom surface <b>130</b> of the chip <b>106</b> to the bonding surface <b>170</b> of the chip receiving slot <b>126</b> in the substrate <b>104</b>, with the air bearing surface <b>128</b> of the chip <b>106</b> substantially at the desired protrusion in the z direction in relation to the air bearing surface <b>110</b> of the substrate <b>104</b>, and with the chip <b>106</b> substantially aligned in the x and y directions with the chip receiving slot <b>126</b> in the substrate <b>104</b>. The chip <b>106</b> is held firmly during the curing operation <b>930</b> to prevent the adhesive from pulling the chip <b>106</b> downward when the adhesive shrinks as it is cured, and to keep the air bearing surface <b>128</b> of the chip <b>106</b> parallel with the air bearing surface <b>110</b> of the substrate <b>104</b>.

The curing operation <b>930</b> may comprise shining at least one U.V. light source on the adhesive for a prescribed period of time, for example 15 seconds. As an example, the U.V. light source may use a 200 watt U.V. lamp (not shown) that has adjustable intensity. The light energy output at the end of a U.V. light guide, for example, the first end <b>532</b> of the first fiber optic U.V. light guide <b>530</b>, may be for example, about one-fifth of the light energy from the U.V. lamp. The optimal U.V. light intensity is a function of the type of adhesive used, and is adjusted to not be so high as to burn the outer surface of the adhesive, but to be high enough to penetrate into the adhesive. The exposure time may be adjusted to be longer or shorter than 15 seconds. Applying U.V. light of the desired intensity for the prescribed time period quickly achieves bonding and fixes the location of the chip <b>106</b>, but for many adhesives (such as Loctite 4303 adhesive), will not fully cure the adhesive. Bond strength generally increases with time for at least 30 days. After the U.V. curing, the adhesive thickness between the bonding surface <b>170</b> of the chip receiving slot <b>126</b> and the bottom surface <b>130</b> of the chip <b>106</b> may vary, for example, from about 5 μm to about 60 μm, with a nominal thickness of about 30 μm, due to manufacturing tolerances of the substrate <b>104</b> and the chip <b>106</b>.

As an example, the curing operation <b>930</b> may include shining at least a first U.V. light source on the adhesive proximate to the front <b>132</b> of the chip <b>106</b> for the prescribed period of time, and shining at least a second U.V. light source on the adhesive proximate to the back <b>134</b> of the chip <b>106</b> for the prescribed period of time. In one example, U.V. light from the first end <b>532</b> of the first fiber optic U.V. light guide <b>530</b> and U.V. light from the first end <b>538</b> of the second fiber optic U.V. light guide <b>536</b> are shined on the adhesive proximate to the front <b>132</b> of the chip <b>106</b> for the prescribed period of time, and U.V. light from the first end <b>544</b> of the third fiber optic U.V. light guide <b>542</b> is shined on the adhesive proximate to the back <b>134</b> of the chip <b>106</b> for the prescribed period of time.

In an alternative embodiment, the curing operation <b>930</b> also includes heating the adhesive, at a temperature and for a time period suitable for the adhesive, to further cure the adhesive. As an example, the module <b>100</b> may be placed in an oven to further cure the adhesive. The temperature used for heating the adhesive and the duration of the heating may be chosen to achieve a desired bond strength while avoiding degradation of any other adhesive bonds (for example, the bond between the chip <b>106</b> and the closure <b>108</b>). As an example, the temperature used for heating the adhesive may be from about 50° C. to about 80° C., and the duration of the heating may be from about 1 hour to about 48 hours. The heating temperature may be determined based on characteristics of the adhesive. Although heating the adhesive may be performed as part of the curing operation <b>930</b>, in other alternative embodiments heating of the adhesive may be performed in an additional curing operation, that for example, could be performed after the grinding operation <b>936</b> (discussed below). Adhesive and process characteristics may be considered to determine whether it is desirable to perform heat curing, and to determine whether to perform heat curing as part of the curing operation <b>930</b> and/or as part of an additional later curing operation. In another alternative embodiment, the curing operation <b>930</b> further includes air and/or anerobic curing of the adhesive. Depending on the extent of the curing performed in the curing operation <b>930</b>, the adhesive may be partially cured, or substantially totally cured, after the curing operation <b>930</b>.

After the curing operation <b>930</b>, the sequence <b>900</b> may also include the operation <b>932</b> of ceasing evacuating air from the hole <b>548</b> in the bottom surface <b>520</b> of the pick-up chuck <b>502</b>, to release the chip <b>106</b> from the pick-up chuck <b>502</b>. Also after the curing operation <b>930</b>, the sequence <b>900</b> may additionally include the operation <b>934</b> of ceasing clamping the substrate <b>104</b> in the substrate seat <b>506</b>, for example by ceasing pressing the substrate front clamp <b>514</b> and the substrate side clamp <b>516</b> against the substrate <b>104</b>.

After the curing operation <b>930</b>, (and after releasing the module <b>100</b> from the substrate seat <b>506</b> and the pick-up chuck <b>502</b>), the sequence <b>900</b> may also include the operation <b>936</b> of grinding the substrate <b>104</b> and the chip <b>106</b> to remove a rear portion of the composite air bearing surface <b>102</b> that includes the portion of the composite air bearing surface <b>102</b> that is above the back <b>120</b> of the substrate <b>104</b>. The portion of the composite air bearing surface <b>102</b> that is removed may be, for example, substantially rectangular. This operation <b>936</b> may be referred to as a taperless grind operation. (However, the surface produced by the grind does not have to be taperless.) More specifically, the taperless grind operation <b>936</b> comprises grinding off a portion of the air bearing surfaces <b>110</b>, <b>128</b> of the substrate <b>104</b> and the chip <b>106</b>, to produce the tail surface <b>157</b> of the chip <b>106</b>, and the tail surface <b>158</b> of the substrate <b>104</b>. The tail surface <b>157</b> of the chip <b>106</b> and the tail surface <b>158</b> of the substrate <b>104</b> are substantially coplanar. The portion that is ground off may be, for example, about 22.5 mm long from the first side <b>122</b> of the substrate <b>104</b> to the second side <b>124</b> of the substrate <b>104</b>, by about 1.75 mm wide (from the back <b>120</b> of the substrate <b>104</b> to the front edge <b>162</b> of the tail surface of the substrate <b>104</b>, and from the back <b>134</b> of the chip <b>106</b> to the front edge <b>161</b> of the tail surface of the chip <b>106</b>), by about 180 μm deep (from the air bearing surface <b>110</b> of the substrate <b>104</b> to the tail surface <b>158</b> of the substrate <b>104</b>).

After the chip <b>106</b> and substrate <b>104</b> have been bonded and are partially cured via U.V. exposure, they may sit at ambient conditions, (for example, ˜20° C. and &lt;30% R.H.), for a period of time, for example 24 hours, prior to the taperless grind operation <b>936</b>. During the taperless grind operation <b>936</b>, the module <b>100</b> is exposed to water in a liquid coolant. The water in the coolant can affect the bond strength and can also cause adhesive swelling that results from adsorption of the liquid by the adhesive. After the taperless grind operation <b>936</b>, the bond strength may drop, for example, by about 40%, and the standard deviation of the bond strength may increase, for example, by about 38%. Additionally, after the taperless grind operation <b>936</b>, the protrusion of the air bearing surface <b>128</b> of the chip <b>106</b> may increase, for example, on average about 0.9 μm. Also, it is possible for some bonds to fail due to motion during the taperless grind operation <b>936</b>. In some embodiments, to reduce the number of bonds that fail during the taperless grind operation <b>936</b>, additional U.V. curing, or heat curing, may be performed prior to performing the taperless grind operation <b>936</b>.

III. Other Embodiments

While the foregoing disclosure shows a number of illustrative embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.